Mark 7:21

For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders,

Christ spoke these words in answer when Pharisees and certain scribes charged His disciples with transgressing the tradition of the elders by eating bread without ceremonial washing of hands. That charge rested on numberless rabbinical rules of purification that professed to guard the law of God but were treated as more sacred than the commandments from Sinai. Life under them became one long struggle against ceremonial defilement, turning attention away from the great principles of the law, and those traditional washings Christ and His disciples did not observe.

Evil thoughts, actions, and traits proceed from within, out of the human heart, as evil fruit from what is inside. That inward source includes pride, vanity, an evil temper, and covetousness coming from the carnal heart when it has not been renewed by Christ's grace. The evil fruit brought forth from within includes the sins listed in the verse and its continuation. Evil thoughts rising from inside the human heart are inspired by Satan. What a person thinks determines what he is.

When light is refused and darkness and unbelief are accepted, the evil heart brings forth its evil. Wicked thoughts are allowed to strengthen and prevail when a person rejects the Word of the Lord and correction of sin and follows his own way and will instead of doing all to the glory of God. Those thoughts grow stronger when a person neglects daily spiritual nourishment from Christ and fails daily to feed on Christ and share His divine nature. The evil heart of unbelief is constantly at war with and resists the purposes of God and tempts souls and turns people away from Christ into forbidden paths.

Such inward evils defile the person and reveal how corrupt the source is from which they spring. Allowed to prevail, they shape conduct into quibbling over technicalities, criticism over lesser matters, accusing brethren, losing a sense of the value of truth, weighing the outside world above light once rejoiced in, and hatred against God for being reproved. Because of this inward danger, God's people must be suspicious of their lower nature and war against fleshly lusts. When the heart is refined, softened, and ennobled, words and actions show the change, and surrender to God brings reliance on His promises, earnest prayer, and determined effort to control speech and conduct.